Merrill A H, Nixon D W, Williams R D
J Lipid Res. 1985 May;26(5):617-22.
Serine palmitoyltransferase [EC 2.3.1.50] catalyzes the first unique reaction of sphingolipid biosynthesis. To determine whether or not different rat tissues are capable of initiating this pathway, its activity was determined for microsomes from rat liver, lung, brain, kidney, intestine, spleen, muscle, heart, pancreas, testes, ovary, and stomach. Serine palmitoyltransferase was found in every tissue, and, when compared to the microsomal glycerol 3-phosphate acyltransferase, the activities correlated directly with their sphingomyelin levels as a percentage of total phospholipids. This suggests that the activities were comparable to expected cellular needs for long-chain bases, if the initial enzymes of glycerolipid and sphingolipid biosynthesis influence the phospholipid composition of cells by determining the relative partitioning of fatty acyl-CoA's toward these two lipid classes. Serine palmitoyltransferase activities were also determined using different fatty acyl-CoA's and were consistently greatest with CoA thioesters of saturated fatty acids with 16 +/- 1 carbon atoms. This suggests that the predominance of 18-carbon long-chain bases in vivo is due to the higher activity of this enzyme with palmitoyl-CoA. Together, these findings indicate a role for serine palmitoyltransferase in regulating both the type and amount of long-chain bases found in tissues.
丝氨酸棕榈酰转移酶[EC 2.3.1.50]催化鞘脂生物合成的首个独特反应。为了确定不同的大鼠组织是否能够启动该途径，测定了大鼠肝脏、肺、脑、肾、肠、脾、肌肉、心脏、胰腺、睾丸、卵巢和胃的微粒体中该酶的活性。在每个组织中均发现了丝氨酸棕榈酰转移酶，并且与微粒体甘油3-磷酸酰基转移酶相比，其活性与鞘磷脂水平（占总磷脂的百分比）直接相关。这表明，如果甘油脂质和鞘脂生物合成的起始酶通过确定脂肪酰辅酶A对这两类脂质的相对分配来影响细胞的磷脂组成，那么这些活性与细胞对长链碱基的预期需求相当。还使用不同的脂肪酰辅酶A测定了丝氨酸棕榈酰转移酶的活性，结果发现，对于含有16±1个碳原子的饱和脂肪酸的辅酶A硫酯，其活性始终最高。这表明体内18碳长链碱基占优势是由于该酶对棕榈酰辅酶A具有更高的活性。这些发现共同表明，丝氨酸棕榈酰转移酶在调节组织中长链碱基的类型和数量方面发挥作用。
